The present invention relates to synchros, more particularly to methods and devices for converting digital signals to a synchro's analog signals.
Synchros are analog electronic devices that have been used for many years, in both military and commercial contexts, for providing angular, positional, and other information pertaining to navigation, communication, detection, weaponry, etc. The noun “synchro” derives from the adjective “synchronous.” Generally speaking, synchros look like electric motors (insofar as including a rotor, a stator, and a shaft) and operate like rotary electrical transformers. A synchro is a type of electrical transformer that measures and sets the angle of a rotating device.
Digital-to-synchro conversion is conversion of digital signals to synchro (analog) signals. Such conversion is necessary in order for synchros to make use of digital signals transmitted by any of various forms of digital (e.g., computer) technology. A digital-to-synchro converter (DSC) is a device frequently used to translate digital user input into signals that actuate a synchro. A conventional digital-to-synchro converter receives binary-coded decimal digital input, and changes it to a three-signal (e.g., three-wire) synchro output representing angular data corresponding to the received binary-coded decimal digital input.
Synchros are common in many commercial, defense, and maritime applications, and are widely used because of their reliability, robustness, and accuracy. For instance, synchros have been used to set the azimuth of satellite dishes, the direction of antennas, the angle of ship rudders, and the trajectory of weapons systems. AC-based synchro control systems are considered to be more suitable than DC-based control systems for many applications. In many large artillery systems, desired target angles are entered through a computer interface, which sends a digital signal to the digital-to-synchro converter; in turn, the DSC generates an equivalent synchro signal to actuate the rotation of the weapon to the proper angle.
Existing compact synchro conversion units are manufactured by few companies. Frequently, commercially available synchros are beset with monopolistic high costs, long procurement lead times, and inadequate accuracy. Only two companies in the world, viz., Data Device Corporation (DDC) and Computer Conversions Corporation (CCC), manufacture compact digital-to-synchro conversion units with an accuracy of 14 bits resolution/110 VAC, and with a maximum driving load of 4.5 VA (39 mA @115 VAC). Conventional digital-to-synchro conversion units offer 14 bits digital resolution with an accuracy of ±4 min error. A product with 16-bits accuracy and 110 VAC range is not available in the market.
Among the technical problems that have been encountered through use of currently available digital-to-synchro converter units (DSCU) are the following: inability to drive a large load (resistive, inductive, or capacitive), e.g., of higher than 4.5 VA; malfunction or total failure; overloading of synchro channels; high temperatures; and, power surges.
Furthermore, existing digital-to-synchro converters use passive electrical (analog) components. In order to generate the synchro signals, these devices rely on precisely manufactured specialty transformers called “Scott-T transformers.” Low-tolerance manufacturing and low-volume orders for Scott-Ts add significant cost to the existing digital-to-synchro devices.
It is therefore desirable to make a digital-to-synchro converter unit that—as compared with current products in the market—is characterized by lower production costs, similarly compact dimensions, higher resolution, greater accuracy, and additional load-driving capability.
Literature instructive on synchros includes, for instance, the Synchro/Resolver Conversion Handbook, Fourth Edition, 1994, Library of Congress Catalog Number 74-77038, Data Device Corporation (DDC), 105 Wilbur Place, Bohemia, New York (electronic version, 125 pages, available in pdf at the DDC website).
Incorporated herein by reference is U.S. patent application publication 2011/0037627 A1, entitled “Modular Units for Synchro-to-Digital Conversion and Digital-To-Synchro Conversion,” published 17 Feb. 2011, application Ser. No. 12/916,020, filed 29 Oct. 2010, inventor Charles J. Hermann.